The invention relates generally to energy management systems and methods for use in connection with locomotives. In particular, the invention relates to an energy tender vehicle and system storing and transferring electrical energy, such as dynamic braking energy or excess prime mover power, produced by locomotives driven by electric traction motors.
FIG. 1A is a block diagram of an exemplary prior art locomotive 100. In particular, FIG. 1A generally reflects a typical prior art diesel-electric locomotive such as, for example, the AC6000 or the AC4400, both or which are available from General Electric Transportation Systems. As illustrated in FIG. 1A, the locomotive 100 includes a diesel engine 102 driving an alternator/rectifier 104. As is generally understood in the art, the alternator/rectifier 104 provides DC electric power to an inverter 106 which converts the AC electric power to a form suitable for use by a traction motor 108 mounted on a truck below the main engine housing. One common locomotive configuration includes one inverter/traction motor pair per axle. Such a configuration results in three inverters per truck, and six inverters and traction motors per locomotive. FIG. 1A illustrates a single inverter 106 for convenience.
Strictly speaking, an inverter converts DC power to AC power. A rectifier converts AC power to DC power. The term converter is also sometimes used to refer to inverters and rectifiers. The electrical power supplied in this manner may be referred to as prime mover power (or primary electric power) and the alternator/rectifier 104 may be referred to as a source of prime mover power. In a typical AC diesel-electric locomotive application, the AC electric power from the alternator is first rectified (converted to DC). The rectified AC is thereafter inverted (e.g., using power electronics such as IGBTs or thyristors operating as pulse width modulators) to provide a suitable form of AC power for the respective traction motor 108.
As is understood in the art, traction motors 108 provide the tractive power to move locomotive 100 and any other vehicles, such as load vehicles, attached to locomotive 100. Such traction motors 108 may be AC or DC electric motors. When using DC traction motors, the output of the alternator is typically rectified to provide appropriate DC power. When using AC traction motors, the alternator output is typically rectified to DC and thereafter inverted to three-phase AC before being supplied to traction motors 108.
The traction motors 108 also provide a braking force for controlling speed or for slowing locomotive 100. This is commonly referred to as dynamic braking, and is generally understood in the art. Simply stated, when a traction motor is not needed to provide motivating force, it can be reconfigured (via power switching devices) so that the motor operates as a generator. So configured, the traction motor generates electric energy which has the effect of slowing the locomotive. In prior art locomotives, such as the locomotive illustrated in FIG. 1A, the energy generated in the dynamic braking mode is typically transferred to resistance grids 110 mounted on the locomotive housing. Thus, the dynamic braking energy is converted to heat and dissipated from the system. In other words, electric energy generated in the dynamic braking mode is typically wasted.
It should be noted that, in a typical prior art DC locomotive, the dynamic braking grids are connected to the traction motors. In a typical prior art AC locomotive, however, the dynamic braking grids are connected to the DC traction bus because each traction motor is normally connected to the bus by way of an associated inverter (see FIG. 1B). FIG. 1A generally illustrates an AC locomotive with a plurality of traction motors; a single inverter is depicted for convenience.
FIG. 1B is an electrical schematic of a typical prior art AC locomotive. It is generally known in the art to employ at least two power supply systems in such locomotives. A first system comprises the prime mover power system that provides power to the traction motors. A second system provides power for so-called auxiliary electrical systems (or simply auxiliaries). In FIG. 1B, the diesel engine (see FIG. 1A) drives the prime mover power source 104 (e.g., an alternator and rectifier), as well as any auxiliary alternators (not illustrated) used to power various auxiliary electrical subsystems such as, for example, lighting, air conditioning/heating, blower drives, radiator fan drives, control battery chargers, field exciters, and the like. The auxiliary power system may also receive power from a separate axle driven generator. Auxiliary power may also be derived from the traction alternator of prime mover power source 104.
The output of prime mover power source 104 is connected to a DC bus 122 which supplies DC power to the traction motor subsystems 124A-124F. The DC bus 122 may also be referred to as a traction bus because it carries the power used by the traction motor subsystems. As explained above, a typical prior art diesel-electric locomotive includes four or six traction motors. In FIG. 1B, each traction motor subsystem comprises an inverter (e.g., inverter 106A) and a corresponding traction motor (e.g., traction motor 108A).
During braking, the power generated by the traction motors is dissipated through a dynamic braking grid subsystem 110. As illustrated in FIG. 1A, a typical prior art dynamic braking grid includes a plurality of contactors (e.g., DB1-DB5) for switching a plurality of power resistive elements between the positive and negative rails of the DC bus 122. Each vertical grouping of resistors may be referred to as a string. One or more power grid cooling blowers (e.g., BL1 and BL2) are normally used to remove heat generated in a string due to dynamic braking.
As indicated above, prior art locomotives typically waste the energy generated from dynamic braking. Attempts to make productive use of such energy have been unsatisfactory. For example, systems that attempt to recover the heat energy for later use to drive steam turbines require the ability to heat and store large amounts of water. Such systems are not suited for recovering energy to propel the locomotive itself. Another system attempts to use energy generated by a traction motor in connection with an electrolysis cell to generate hydrogen gas for use as a supplemental fuel source. Among the disadvantages of such a system are the safe storage of the hydrogen gas and the need to carry water for the electrolysis process. Still other prior art systems fail to recapture the dynamic braking energy at all, but rather selectively engage a special generator that operates when the associated vehicle travels downhill. One of the reasons such a system is unsatisfactory is because it fails to recapture existing braking energy.
Therefore, there is a need for an tender vehicle that can be used to capture and store the electrical energy, including electrical energy generated in the dynamic braking mode. There is further a need for such a tender that selectively regenerates the stored energy for later use. There is also a need for an energy tender vehicle that is equipped with a traction motor system. There is also a need for an energy tender vehicle that can operate in a wireless or semi-wireless configuration, and at any position in a train.
In one aspect, the invention relates to a hybrid energy locomotive system for use in connection with a train. The system includes a locomotive having a plurality of locomotive wheels. A locomotive traction motor is associated with one of the plurality of locomotive wheels. The locomotive traction motor has a first rotatable shaft mechanically coupled to the one of the plurality of locomotive wheels. An electric power source selectively supplies locomotive electric power to the locomotive traction motor. The locomotive traction motor is operable in response to the locomotive electric power to rotate the first rotatable shaft and to drive the one of the plurality of locomotive wheels. The locomotive traction motor further has a dynamic braking mode of operation in which the locomotive traction motor generates electrical energy in the form of electricity. An electrical energy capture system is in electrical communication with the locomotive traction motor. The electrical energy capture system selectively stores electrical energy generated in the dynamic braking mode and selectively provides secondary electric power from the stored electrical energy. As such, the electrical energy capture system selectively supplements the locomotive electric power with the secondary electric power. An energy tender vehicle is coupled to the locomotive. The energy tender vehicle comprises a plurality of energy tender wheels. An energy tender traction motor is associated with one of the plurality of energy tender wheels. The energy tender traction motor has a second rotatable shaft mechanically coupled to the one of the plurality of energy tender wheels wherein the electrical energy capture system provides a first portion of the secondary electric power to the energy tender traction motor. The energy tender traction motor is operable in response to the provided first portion of the secondary electric power to rotate the second rotatable shaft and to drive the one of the plurality of energy tender wheels. And the electrical energy capture system provides a second portion of the secondary electric power to supplement the locomotive electric power supplied to the locomotive traction motor.
In another aspect, the invention relates to an energy tender for use in connection with a hybrid energy locomotive system propelling a train. The train includes a locomotive, an engine, a power converter driven by the engine for providing primary electric power, a traction bus coupled to the power converter and carrying the primary electric power, and a locomotive traction system coupled to the traction bus. The locomotive traction system has a motoring mode and a dynamic braking mode. The locomotive traction system propels the train in response to the primary electric power in the motoring mode. The locomotive traction system generates electrical energy in the dynamic braking mode. The energy tender comprises an energy tender vehicle coupled to the locomotive. An electrical energy storage system selectively captures the electrical energy generated by the locomotive traction system in the dynamic braking mode. The electrical storage system selectively transfers a first portion of the captured electrical energy to the locomotive traction system to augment the primary electric power in the motoring mode. An energy tender converter is electrically coupled to the energy storage system such that the energy storage system selectively transfers a second portion of the captured electricity to the energy tender converter. The energy tender converter is responsive to the transferred second portion of the captured electricity to provide energy tender drive power. An energy tender traction system is associated with the energy tender vehicle. The energy tender traction system is electrically coupled to the energy tender converter and propels the energy tender vehicle in response to the energy tender drive power.
In still another aspect, the invention relates to a hybrid energy locomotive system for propelling a train on a track. The system comprises an engine. A power converter driven by the engine provides primary electric power. A traction bus coupled to the power converter carries the primary electric power. A locomotive traction system is coupled to the traction bus. The locomotive traction system has a motoring mode and a dynamic braking mode. The locomotive traction system propels the train in response to the primary electric power in the motoring mode. The locomotive traction system generates electrical energy in the dynamic braking mode. An electrical energy storage system is coupled to the traction bus. The electrical energy storage system selectively captures the electrical energy generated by the locomotive traction system in the dynamic braking mode and selectively transfers a first portion of the captured electrical energy to the locomotive traction system to augment the primary electric power in the motoring mode. An energy tender vehicle coupled to the locomotive houses the energy storage system.
In yet another aspect, the invention relates to a hybrid energy locomotive system. The system comprises a locomotive. An electric power source supplies primary electric power. A locomotive traction motor propels the locomotive in response to the primary electric power. The locomotive traction motor has a dynamic braking mode of operation wherein the locomotive traction motor generates electricity. An energy capture system is in electrical communication with the locomotive traction motor. The energy capture system selectively stores electricity generated by the locomotive traction motor in the dynamic braking mode and selectively provides secondary electric power from the stored electricity. An energy tender vehicle is mechanically coupled to the locomotive. The energy tender vehicle has an energy tender traction motor receiving the secondary electric power provided by the energy capture system and propelling the energy tender vehicle in response to the secondary electric power. The energy tender traction motor and the locomotive traction motor cooperate to propel a consist comprising the locomotive and the energy tender vehicle.
In another aspect, the invention relates to a method of operating a hybrid energy locomotive system. The hybrid energy locomotive system includes a locomotive and an energy tender vehicle mechanically coupled to the locomotive. The locomotive has an electric power source supplying primary electric power to a locomotive traction motor system. The locomotive traction motor system operates in a locomotive motoring mode of operation in response to the supplied primary electric power to propel the locomotive. The energy tender vehicle includes an energy tender traction motor system having an energy tender motoring mode of operation and an energy tender dynamic braking mode of operation. The energy tender vehicle also includes an energy storage system electrically coupled to the energy tender traction motor system. The method comprises supplying the primary electric power to the locomotive traction motor system. The locomotive traction motor system is operated in the locomotive motoring mode in response to the supplied primary electric power. The energy tender traction motor system is operated in the energy tender dynamic braking mode when the locomotive traction motor system is operating in the locomotive motoring mode. Dynamic braking electrical energy is generated when the energy tender traction motor system operates in the energy tender dynamic braking mode. The dynamic braking electrical energy generated when the energy tender traction motor system operates in the energy tender dynamic braking mode is stored in the energy storage system. Secondary electric power from the energy storage system is supplied to the energy tender traction motor system when the energy tender traction motor system operates in the energy tender motoring mode. The secondary electric power is derived from the dynamic braking electrical energy stored in the energy storage system. As such, the energy storage system is charged by operating the energy tender traction motor system in the dynamic braking mode and discharged by operating the energy tender traction motor in the motoring mode.
In still another aspect, the invention relates to an energy tender, other than a locomotive, for use with a train consist. The consist includes a diesel-electric locomotive having locomotive engine driving a locomotive power converter for supplying a prime mover electric power. The energy tender comprises an energy tender vehicle having a plurality of energy tender wheels. A traction motor system drives one of the plurality of energy tender wheels in response to electric input power. The traction motor system has a dynamic braking mode of operation generating electrical energy in the form of electricity. An energy capture system on the energy tender vehicle is in electrical communication with the traction motor system. The energy capture system selectively stores electrical energy generated in the dynamic braking mode. an energy converter system selectively provides tender electric power from the electrical energy stored by the energy capture system. The tender electric power is supplied to the traction motor system to selectively provide at least part of the electric input power for driving the plurality of energy tender wheels.